Elon Musk’s brain chip startup Neuralink—which aims to create an interface allowing for humans to control electronic devices via brainwaves—is facing a slew of animal abuse accusations.

New disturbing claims were made on Monday in a complaint filed by the Physicians Committee for Responsible Medicine (PCRM) to the U.S. Department of Agriculture (USDA). The PCRM accused Musk’s company and its partners at the University of California, Davis of causing “extreme suffering” in test subjects. The subjects, which were mainly primates, allegedly “had their brains mutilated in shoddy experiments and were left to suffer and die,” according to the complaint per the Guardian.

PCRM further stated that Neuralink relied on a substance called “BioGlue” that allegedly mutilated the monkeys’ brains. The complaint goes on to describe how the animals experienced debilitating psychological side effects from BioGlue, including self-mutilating acts like tearing off their own fingers.

“Animals at Neuralink are respected and honored by our team,” Neuralink wrote on its Twitter account. “Without proper context, information from medical records and study data can be misleading.”

The company responded further in a lengthy blog post, where it broke down its experimentation process and denied the accusations. The post claimed animals were always carefully observed, and that a vast team of “veterinarians, veterinary technicians, behaviorists, enrichment technicians, and animal care specialists who provide positive reinforcement training and around the clock care for our animals” were employed.

The post also stated that the monkeys who did perish during Neuralink experiments were laid to rest via a “terminal procedure,” where they were euthanized “humanely” post-surgery. 

“We also look forward to a day where animals are no longer necessary for medical research,” the statement continued. “Yet our society currently relies on medical breakthroughs to cure diseases, prevent the spread of viruses, and create technology that can change how people are able to interact with the world. However, if animals must be used in research in the meantime, their lives and experiences should be as vital and naturalistic as possible.”

The animal abuse accusations arrive after the neurotech company shared a video last April of a monkey using a Neuralink chip to play Pong with its mind. “You can’t see where the implant is and he’s a happy monkey,” Musk initially said when he unveiled the technology last February. “We have the nicest monkey facilities in the world. We want them to play mind-Pong with each other. That would be pretty cool.”